Computer-assisted surgery (CAS) is a generally known and practically used surgery method, wherein a surgical operation is planned and/or conducted using a 3D model of a body section to be treated. In particular, the 3D model can be used for planning the steps of a surgical operation, e.g., the motion and adjustment of surgical tools or implants, for monitoring the surgical operation, or for constructing a real 3D implant. Typically, the 3D model can be generated on the basis of image data collected with medical imaging of a patient, e.g., by an image registration of computer tomography (CT) data of the body section with CT data of a certain portion of the body section.
Image registration (or: registration, image alignment) is a data processing method, wherein different sets of image data are transformed into one common coordinate system. The different sets of real image data are collected e.g., with different sensors, at different times and/or from different viewpoints. Typically, a first set of image data (target image) is adapted to a second set of image data (reference image), both covering the same region of investigation. The transformation or adaptation can be performed manually, interactively, semi-automatically or automatically. The automatic registration uses a numerical registration process (registration algorithm). Conventional applications of image registration are restricted to the transformation of data covering the same region of investigation.
If image data of a complete body section are not available, e.g., due to a destruction after an accident or a disease, or due to a congenital defect, generating model data for a 3D model requires a completion of the collected real image data with reconstructed data. As an example, CAS applications in Cranio-Maxillar-Facial surgery (CMF surgery) may require a reconstructed patient 3D model for obtaining complete skull image data. With one-sided defects, completion of collected data can be obtained by a simple mirroring of the healthy half to the pathological half of the skull. However, with defects on both sides of the skull or with asymmetric body sections, a reconstruction is required, which conventionally comprises manual or semi-automatic procedures using reference points and reference planes in a reference image selected by a surgeon (see S. Zachow et al. in “Journal of Computing and Information Technology—CIT 14” vol. 1, 2006, p. 53-64). Those conventional procedures are time-consuming and prone to failures. As a further disadvantage, the quality of the 3D model thus obtained essentially depends on the experience of the surgeon.